以鈣矽石漿液捕捉二氧化碳之研究

Abstract

本研究探討在常壓下以二氧化碳和鈣矽石漿液產生碳酸鈣而捕捉二氧化碳的可行性。考慮的操作變數包含漿液固體含量、反應溫度、攪拌轉速、二氧化碳流量、溶液pH值及漿液之組成。使用礦石粒徑為22μm。 由實驗結果觀察得知，攪拌轉速和二氧化碳流量對反應沒有影響。鈣矽石轉化率隨漿液固體含量增加而降低。反應溫度有一最佳值，約為60oC。及固體含量0.4%的去離子水漿液通入一大氣壓的二氧化碳，600分鐘後轉化率可達43.9%； 600分鐘後，停止二氧化碳通入並添加氫氧化鈉使pH值上升至9，可將轉化率提升至56.8%。使用0.64M碳酸氫納�1M氫氧化鈉溶液配置漿液，可以提升轉化率，轉化率可達34.2%。 鈣矽石在水相中的碳酸化反應包括二氧化碳的水解，鈣矽石的溶解及碳酸鈣的生成，其反應速率決定步驟為鈣矽石的溶解。 使用1M的醋酸溶液先將鈣矽石溶解2小時，再使用氫氧化鈉中和醋酸並通入二氧化碳，可得到84.5%的碳酸化轉化率，但此程序會消耗大量醋酸和氫氧化鈉。

The feasibility of using the slurry of wollastonite to capture CO2 to form CaCO3 at 1atm was studied. The effects of the operation variables, including the solid content, reaction temperature, stirrer speed, flow rate of carbon dioxide, solution pH, and solution chemistry on the carbonation of wollastonite(22μm) were investigated. The stirrer speed and the flow rate of carbon dioxide affected little the carbonation reaction of wollastonite. The conversion decreased with increasing solid content of the slurry. The optimum reaction temperature was about 60oC. A conversion of 43.9% was achieved when the slurry of wollastonite (slurry solid content: 0.4% in deionized water) was reacted at 60oC and 1atm for 600minutes; the conversion was raised to 56.8% when NaOH was then added to raise the solution pH to 9. The use of 0.64M NaHCO3/1M NaCl Solution instead of deionized water increased the extent of carbonation. The conversion was raised to 34.2%. The carbonation of wollastonite in aqueous phase involved the hydrolysis of carbon dioxide, the dissolution of wollastonite, and the precipitation of calcium carbonate. The dissolution of wollastonite was found to be the rate determining step. A conversion of 84.5% was achieved when wollastonite was dissolved in 1M acetic acid for 2 hours and NaOH was then added to keep pH at 9 while CO2 was bubbled; but this process consumed agreat amounts of acetic acid caustic soda.